In a method known from practice for suppressing multipath interference in an FM or VHF receiver, known as the ADA (autodirectional antenna) method, the new signal is generated by a suitable linear combination of at least two antenna signals. The term “diversity method” refers to a method for suppressing multipath interference in an FM or VHF receiver by switching between different antennas. The switching is performed here as a function of the particular reception field strength and signal quality. In the broadest sense, the diversity method could be considered a special case of the ADA method in which only one of the coefficients of the linear combination is not equal to zero. In addition, it is known from practice that the antenna signals of an FM or VHF receiver may be used for RDS (Radio Data System) activities.
U.S. Pat. No. 5,345,602 describes a VHF radio receiver which mixes a plurality of antenna signals with a locally generated oscillator signal and subsequently adds them up. On the basis of the resulting signal, the playback signal is then generated. At the same time, the receiver switches briefly to alternative transmission frequencies of the set transmitter in periodic intervals in a manner that is not perceptible to the human ear to determine the reception quality of these alternative transmission frequencies and stores them. If the reception quality of the transmission frequency originally set is inadequate, it is then possible to switch rapidly to the best of the alternative transmission frequencies in a manner that cannot be detected by the listener.
In addition to these AF (alternate frequency) tests, which are described in U.S. Pat. No. 5,345,602, and the PI (program identification) tests, RDS activities frequently also include monitoring of TMCs (traffic message channels).
In the case of the VHF radio receiver known from U.S. Pat. No. 5,345,602 and the method described in this conjunction, generation of the playback signal is always based on a new signal generated from a plurality of antenna signals, even when at the moment there is no multipath interference or fading effects. In addition, with respect to the known VHF radio receivers, it should be pointed out that very little time is available for the RDS activities if they are not to be perceived by a listener because the RDS processing is based on the same signal as that used in generation of the playback signal. For example, the duration of the AF test performed must not exceed a few milliseconds.